1. Field of Invention
The present invention relates to a layer 2 link handler and layer 2 link path connection method. At present there is a growing demand for TCP/IP communication represented by LAN or Internet, etc., and it is desired that its communication speed be speeded up.
As one means for speeding up TCP/IP communication, systems are being adopted that employ an ATM (asynchronous transfer mode) network or other wide-area network as the low-level physical layer of the IP communication. This invention concerns a handler and layer 2 link path connection method that handle layer 2 link paths between such layer 3 IP communication and the ATM or other wide-area network of the low-level physical layer.
2. Description of the Prior Art
There are two types of path connections in an ATM network: an SVC (switched virtual connection) path, in which the user connects the path by specifying the other party every time communication is begun, and a PVC (permanent virtual connection) path, in which the path to the other party of the connection is set in advance.
An SVC (switched virtual connection) path is like a path connected in the present telephone network, according to the telephone number of the other party that is specified by the user. The ATM path is set according to the user side's specification of the other party's address on the ATM network, and it is set between the user side and the ATM exchange by exchanging, by a protocol known as I.2931, control signals (signaling) for ATM path setting, including a path connection request.
A PVC (permanent virtual connection) path is a path that is continuously set by a fixed path with the other party. Signaling is not needed to set a path between the user side and the ATM exchange; the path is set in advance by the operator on the ATM network side.
There are still few devices that support connections using an SVC (switched virtual connection) path for the connection between the user-side device and the ATM network-side device. At present, there are many that use a PVC (permanent virtual connection) path for the connection between the user-side device and the ATM network-side device. Because there is expected to be a growing demand for ordinary connection communication service, it is anticipated that connection by a PVC (permanent virtual connection) path will continue in the future as the main mode of connection.
FIG. 26 shows an example of connections using PVC (permanent virtual connection) paths between the user-side device and the device of network service provider (NSP) side. In this mode of connection, the connection destination of each user-side device is fixed, and one cannot select and connect to an arbitrary network service provider (NSP).
Many PVC (permanent virtual connection) paths are concentrated in the connection opening of each network service provider (NSP), and each network service provider (NSP) must handle many PVC (permanent virtual connection) paths. Because each PVC (permanent virtual connection) path must be assigned a fixed band at all times despite the concentration of many PVC (permanent virtual connection) paths, it is difficult to do traffic line collection.
FIG. 27 shows the frame composition if IP (Internet protocol) frame data is transmitted along ATM paths such as the aforesaid PVC (permanent virtual connection) paths. As shown in this diagram, a layer 3 IP frame is encapsulated in a layer 2 PPP (point-to-point protocol) and is broken up by AAL5 (ATM adaptation layer type 5) into ATM cells of the physical layer.
A connection by PPP protocol is an example of a connection-oriented layer 2 link, and a 1-to-1 link is set from the user-side device to the device on the network service provider (NSP) side. Only one PPP link can be set on a single PVC (permanent virtual connection) path on the ATM network.
If data communication service, etc. by IP frames is to supplied by connection by such a PVC (permanent virtual connection) path between the user side and the network service provider (NSP) side, the following will be required of the equipment on the ATM network side.
If there is just one network service provider (NSP) to which a connection request is made by one user-side device, then it suffices to set one PVC (permanent virtual connection) path between each user-side device and device on the network service provider (NSP) side.
If each user wishes to make connections to multiple network service providers (NSPs), then there will be cases in which the user contracts simultaneously with multiple network service providers (NSPs) and chooses which network service provider (NSP) to connect to depending on the content of the communication or whether it is for private or commercial use.
Also, depending on the country, it is required that carriers offer users fair access open points to network service providers (NSPs), such as prohibiting network service provision by carriers or imposing the obligation that each carrier fairly provide access to the network service provider (NSP) the user wants.
For the above reasons, it is necessary that the ATM-side equipment be able to fairly access any network service provider (NSP) as demanded by the user, and it is required that a switching connection be made to any network service provider (NSP) the user wants, even if the user and the network service provider (NSP) are connected by a PVC (permanent virtual connection) path.
When a PVC (permanent virtual connection) path is individually set to a network service provider (NSP) from each user, the number of PVC (permanent virtual connection) paths connected to a network service provider (NSP) becomes enormous, so the equipment on the side of each network service provider (NSP) must be able to handle an enormous number of PVC (permanent virtual connection) paths.
Traffic line collection is difficult to do because, despite the concentration of traffic in the equipment on the side of a network service provider (NSP), a single PVC (permanent virtual connection) path has a 1-to-1 correspondence with the PPP link, and the channel identifiers on the ATM layer are different for each PVC (permanent virtual connection) path.